An apparatus for reproducing data from and recording data on optical disks, such as digital video disk (DVD) combo disks, compact disk-recordable (CD-R) disks, or compact disk-rewritable (CD-RW) disks, may emit a laser beam onto a track of a disk, pick up the reflected light, and read audio or video information included in the reflected light. This recording data may include audio/video information in some applications. Audio or video information recorded on spiral tracks of a disk is typically coded into pits and lands or marks and spaces on the disks.
An apparatus for reproducing and recording data may perform optimum power control (OPC) to appropriately record wanted information on an optical disk using a laser diode (LD). The optimum laser power needed to appropriately record information on the optical disk may be found using the OPC operation, in which a laser beam is emitted on a power calibration area (PCA) located inside a lead-in region of the optical disk. The power of the laser beam may be varied from high power to low power during the OPC operation.
The amount of laser power required to record data on a disk typically varies depending on the type of reproducing/recording apparatus and type of disk. Furthermore, the amount of laser power required to record data is often different for different locations of a disk. For example, the amount of laser power for a CD-R disk recorded at a 2× speed is kept within a power window of about 2 mW in the range of 8-10 mW. If data is recorded on the disk within the power range of 8-10 mW, an appropriate sized pit may be formed. However, if the amount of laser power does not fall within the range of 8-10 mW, inappropriate sized pits may be formed. In addition, the size of a laser spot used for recording data or optical quality can be affected by temperature or external environmental factors. As such, if the pit formed on the optical disk is inappropriate due to the amount of laser power or other external factors, an error occurs while reproducing data, and thus normal audio/video data typically cannot be reproduced.
To perform OPC, a conventional optical disk reproducing/recording apparatus uses a radio frequency signal RRF generated from a picked up signal, as illustrated in FIG. 1. The amount of laser power may be controlled by detecting a land-level A1, which is the peak voltage, and a pit-level A2, which is the minimum voltage, from the radio frequency signal RRF, calculating power control information β using Equation 1 below, and then compensating direct current (DC) offset based on the calculated power control information β.β=(A1+A2)/(A1−A2)  (1)
For example, when β<0 as illustrated in FIG. 1A, which is the under-power state, the pit is shallow and thus the power is increased to become as illustrated in FIG. 1B. Also, when β>0 as illustrated in FIG. 1C, which is the over-power state, the pit is deep and thus the power is decreased to become as illustrated in FIG. 1B. Commonly, within ±4% of is regarded as normal to be compatible with various types of media.
However, the land-level A1 and the pit-level A2 can be inaccurately detected due to, for example, noise from the external environment, in the conventional method of performing OPC in the optical reproducing/recording apparatus. Also, even if the land-level A1 and the pit-level A2 are accurately detected, a complex circuit to calculate β using Equation 1 may be required.